1. Field of the Invention
This invention relates to a plated material, and more particularly, to a plated material having an electrically conductive plating and used for forming a contact for an electrical connector, and a contact formed by using the same.
2. Description of the Prior Art
Various types of connectors have been used for making connections in electronic devices. A gold plated material is used for making contacts for electronic parts, such as connectors, owing to its corrosion resistance and electrical conductivity, particularly when highly reliable contacts have to be made. Gold is, however, expensive, and adds to the cost of making contacts. It is, therefore, usual to form a gold plating with as small a thickness as possible. A gold plating having a small thickness, however, has a large number of pinholes through which corrosion is likely to occur to a substrate metal. It is, therefore, usual to give treatment for preventing such corrosion by, for example, forming a film of chromic acid, or a layer of an organic substance on a gold plating.
Another problem of a gold plating having a small thickness lies in its wear leading to the loss of gold, as is often the case with gold platings on connectors which are brought into engagement, or contact repeatedly for the operation of a device, such as an IC card. In a gold plating, the sealing of pinholes is effectively employed for preventing corrosion, but is hardly effective for preventing any such wear. A film or layer formed for preventing corrosion is not satisfactory for preventing any such wear. A lubricant oil is applied to the gold plating for protecting it against wear, but is not satisfactory for corrosion resistance, since corrosive gas molecules are so small as to pass through a film of oil.
Therefore, there has been a demand for a gold plated material having a surface treated for corrosion resistance and lubrication for wear resistance as well.
It is, therefore, an object of this invention to provide a plated material having a high protective power in a corrosive environment, and maintaining a constantly low contact resistance.
It is another object of this invention to provide a plated material having a lubricating property to impart a high level of wear resistance to a connector which is repeatedly engaged with another.
It is still another object of this invention to provide a plated material having a lubricating property to reduce a frictional force acting on a connector when it is engaged with another, or disengaged therefrom.
It is yet another object of this invention to provide a connector formed by using a plated material as defined above.
According to this invention, there is provided a plated material comprising a substrate, a plating formed on a surface selected from the substrate and an undercoating formed on the substrate, a bonding layer of an organic substance formed on the plating, and a lubricating layer formed on the bonding layer. The organic substance is an organic compound capable of combining chemically with a component of the plating. The lubricating layer consists essentially of a fluid film of a high molecular mass.
The bonding layer of an organic substance preferably consists essentially of a monomolecular film thereof. The organic substance is preferably an organic compound having a thiol (xe2x80x94SH) group.
The substrate is preferably of an electrical conductor, and more preferably of a metal. The metal is preferably at least one of copper, a copper alloy, iron, stainless steel, and a combination thereof.
The plating preferably contains gold, and more preferably consists essentially of a metal selected from gold-cobalt and gold-nickel alloys. The plating is preferably formed on the undercoating, and the undercoating is preferably of a metal of nickel or a nickel alloy.
According to this invention, there is also provided a contact for a connector comprising a substrate, a plating formed on a surface selected from the substrate and an undercoating formed on the substrate, a bonding layer of an organic substance formed on the plating, and a lubricating layer formed on the bonding layer. The organic substance is an organic compound capable of combining chemically with a component of the plating. The lubricating layer consisting essentially of a fluid film of a high molecular mass.
The bonding layer of an organic substance has a sufficiently small thickness to produce a tunnel effect. This and the fluidity of the lubricating layer ensure that the plated material, or contact maintain a low initial contact resistance.